Make Own Chocolate Cake Recipe

AHow do I turn my own base vanilla cake recipe into chocolate? Every good from scratch cupcake/cake shop I've been to have the same texture/crumb for all their cakes. I can only conclude they have the same base recipe for all their cakes.

So do I substitute some of the flour for cocoa powder? If so how much? Thank you.

AThe best thing to do is experiment with your own recipes.
I'm sure other bakeries are using different recipes for each flavor, they just use similar formulas & mixing techniques. All of my cake recipes have pretty close to the same texture because I've experimented with the ingredients, and converted (if needed) the mixing technique to achieve the texture I wanted.
Get in the kitchen and start mixing, making notes of what you do, so when you get what you want, you've got your own recipes.

The best thing to do is experiment with your own recipes.
I'm sure other bakeries are using different recipes for each flavor, they just use similar formulas & mixing techniques. All of my cake recipes have pretty close to the same texture because I've experimented with the ingredients, and converted (if needed) the mixing technique to achieve the texture I wanted.
Get in the kitchen and start mixing, making notes of what you do, so when you get what you want, you've got your own recipes.

Thank you. I wanted to make sure there wasn't some sort of method before I start experimenting. My recipes so far are very different but don't yield the same crumb/texture and I want to change that.

AWish I could help more, but experimenting is all I can suggest. I have been baking most of my life, but I still bought baking science books to learn more about the interactions of ingredients and how they affect the outcome. (I'm totally a nerd for that stuff :) )
So start out substituting maybe 3-4oz of cocoa for flour and see what happens. Remember that Dutch cocoa is more alkaline, & regular process cocoa (Hershey's) is more acidic, so you will need a small amount of baking soda to neutralize that acid.

AI appreciate any and all of your help. I highly look up to pros or anyone who knows what they're doing. That bit of information about the cocoa powder and books help greatly too. I definitely need to learn the science part more which is why I've been thinking about pastry school. Baking is my passion and dream.